ABSTRACT—Our study was undertaken to determine whether human recombinant interferon α(rIFNα), γ(rIFNγ), and tumor necrosis factor α(rTNFα) exert an effect on the HLA‐A, B, C expression of human liver cell lines. The HLA‐A, B, C expression was assayed by immunoperoxidase staining and enzyme‐linked immunosorbent assay. rIFNα and γ enhanced the HLA‐A, B, C expression of the three cell lines tested, Chang cells, SK‐Hep‐1, and PLC/PRF/5. The activity of rIFNγ proved more than 8000 times more potent than that of rIFNα in Chang cells, 30 times in SK‐Hep‐1, and 20 times in PLC/PRF/5, respectively. rTNFα also enhanced the HLA‐A, B, C expression of the three cell lines. The enhancement of HLA‐A, B, C expression by rIFNα and γ reached a peak on day 3, and that by rTNFα on day 5. These findings suggest that IFNα, IFNγ, and TNFα may play similar roles in enhancement of HLA‐A, B, C expression of hep